Regulation of seed coat mucilage production and modification in Arabidopsis

Brassica napus BnaA09.MYB52 enhances seed coat mucilage accumulation and tolerance to osmotic stress during seed germination in Arabidopsis thaliana

Seed coat mucilage plays an important role in promoting seed germination under adversity. Previous studies have shown that Arabidopsis thaliana MYB52 (AtMYB52) can positively regulate seed coat mucilage accumulation. However, the role of Brassica napus MYB52 (BnaMYB52) in accumulation of seed coat mucilage and tolerance to osmotic stress during seed germination remains largely unknown. We cloned the BnaA09.MYB52 coding domain sequence from B. napus cv ZS11, identified its conserved protein domains and elucidated its relationship with homologues from a range of plant species. Transgenic plants overexpressing BnaA09.MYB52 in the A. thaliana myb52-1 mutant were generated through Agrobacterium-mediated transformation and used to assess the possible roles of BnaA09.MYB52 in accumulation of seed coat mucilage and tolerance to osmotic stress during seed germination. Subcellular localization and transcriptional activity assays demonstrated that BnaA09.MYB52 functions as a transcription factor. RT-qPCR results indicate that BnaA09.MYB52 is predominantly expressed in roots and developing seeds of B. napus cv ZS11. Introduction of BnaA09.MYB52 into myb52-1 restored thinner seed coat mucilage in this mutant to levels in the wild type. Consistently, expression levels of three key genes participating in mucilage formation in developing seeds of myb52-1 were also restored to wild type levels by overexpressing BnaA09.MYB52. Furthermore, BnaA09.MYB52 was induced by osmotic stress during seed germination in B. napus, and ectopic expression of BnaA09.MYB52 successfully corrected sensitivity of the myb52-1 mutant to osmotic stress during seed germination. These findings enhance our understanding of the functions of BnaA09.MYB52 and provide a novel strategy for future B. napus breeding.

Research overview on the genetic mechanism underlying the biosynthesis of polysaccharide in tuber plants

Tuber plants are of great significance in the world as human food crops. Polysaccharides, important metabolites in tuber plants, also serve as a source of innovative drugs with significant pharmacological effects. These drugs are particularly known for their immunomodulation and antitumor properties. To fully exploit the potential value of tuber plant polysaccharides and establish a synthetic system for their targeted synthesis, it is crucial to dissect their metabolic processes and genetic regulatory mechanisms. In this article, we provide a comprehensive summary of the basic pathways involved in the synthesis of various types of tuber plant polysaccharides. We also outline the key research progress that has been made in this area in recent years. We classify the main types and functions of tuber plant polysaccharides and analyze the biosynthetic processes and genetic regulation mechanisms of key enzymes involved in the metabolic pathways of starch, cellulose, pectin, and fructan in tuber plants. We have identified hexokinase and glycosyltransferase as the key enzymes involved in the polysaccharide synthesis process. By elucidating the synthesis pathway of polysaccharides in tuber plants and understanding the underlying mechanism of action of key enzymes in the metabolic pathway, we can provide a theoretical framework for enhancing the yield of polysaccharides and other metabolites in plant culture cells. This will ultimately lead to increased production efficiency.

Disruption of the Arabidopsis Acyl-Activating Enzyme 3 Impairs Seed Coat Mucilage Accumulation and Seed Germination

The Acyl-activating enzyme (AAE) 3 gene encodes an oxalyl-CoA synthetase that catalyzes the conversion of oxalate to oxalyl-CoA as the first step in the CoA-dependent pathway of oxalate catabolism. Although the role of this enzyme in oxalate catabolism has been established, its biological roles in plant growth and development are less understood. As a step toward gaining a better understanding of these biological roles, we report here a characterization of the Arabidopsis thaliana aae3 (Ataae3) seed mucilage phenotype. Ruthidium red (RR) staining of Ataae3 and wild type (WT) seeds suggested that the observed reduction in Ataae3 germination may be attributable, at least in part, to a decrease in seed mucilage accumulation. Quantitative RT-PCR analysis revealed that the expression of selected mucilage regulatory transcription factors, as well as of biosynthetic and extrusion genes, was significantly down-regulated in the Ataae3 seeds. Mucilage accumulation in seeds from an engineered oxalate-accumulating Arabidopsis and Atoxc mutant, blocked in the second step of the CoA-dependent pathway of oxalate catabolism, were found to be similar to WT. These findings suggest that elevated tissue oxalate concentrations and loss of the oxalate catabolism pathway downstream of AAE3 were not responsible for the reduced Ataae3 seed germination and mucilage phenotypes. Overall, our findings unveil the presence of regulatory interplay between AAE3 and transcriptional control of mucilage gene expression.

Fruit development and ripening orchestrating the biosynthesis and regulation of Lycium barbarum polysaccharides in goji berry

Lycium barbarum polysaccharides (LBPs) are the primary bioactive components in fruits of L. barbarum, commonly known as goji berry. Despite significant progress in understanding the chemical structures and health benefits of LBPs, the biosynthesis and regulation of LBPs in goji berry remains largely unknown. In this study, physiological indicators, including LBPs, were monitored in goji berry during fruit development and ripening (FDR), suggesting that pectin might be the major component of LBPs with increased content reaching 235.8 mg/g DW. Proteomic and transcriptomic analysis show that 6410 differentially expressed genes (DEGs) and 2052 differentially expressed proteins (DEPs) were identified with overrepresentation of flavonoids and polysaccharides-related gene ontology (GO) terms and KEGG pathways. Weighted gene co-expression network analysis (WGCNA) showed that LBPs coexpress with genes involved in pectin biosynthesis (LbGALS3, LbGATL5, LbQUA1, LbGAUT1/4/7, LbRGGAT1, LbRRT1/7, and LbRHM2), modification (LbSBT1.7), and regulation (LbAP2, LbGL2 LbTLP2, LbERF4, and LbTTG2), as well as with novel transcription factors (LbSPL9 and LbRIN homologs) and glycosyltransferases. Transgenic hairy roots overexpressing LbRIN validated that LbRIN modulate the expression of WGCNA-predicted regulators, including LbERF4, LbTTG2, and LbSPL9. These findings suggest that the biosynthesis and regulation of LBPs is conserved partially to those in Arabidopsis pectin. Taken together, this study provides valuable insights into the biosynthesis and regulation of LBPs, which can facilitate future studies on synthetic biology applications and genetic improvement of LBPs.